{"cve":"CVE-2026-34827","nvd":{"published":"2026-04-02T18:16:33.490","modified":"2026-07-24T21:10:00.143","status":"Modified","description":"Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name=\"...\" using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400","CWE-407","CWE-770"],"references":["https://github.com/rack/rack/security/advisories/GHSA-v6x5-cg8r-vv6x","https://access.redhat.com/security/cve/CVE-2026-34827","https://bugzilla.redhat.com/show_bug.cgi?id=2454501","https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34827.json"],"products":["rack:rack"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-34827","score":0.00494,"percentile":0.42432,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-v6x5-cg8r-vv6x","url":"https://osv.dev/vulnerability/GHSA-v6x5-cg8r-vv6x","summary":"Rack's multipart header parsing allows Denial of Service via escape-heavy quoted parameters","modified":"2026-09-10T03:50:44.804498177Z","packages":[{"ecosystem":"RubyGems","name":"rack","purl":"pkg:gem/rack","ranges":[">=3.0.0.beta1 <3.1.21"],"fixed":["3.1.21"]},{"ecosystem":"RubyGems","name":"rack","purl":"pkg:gem/rack","ranges":[">=3.2.0 <3.2.6"],"fixed":["3.2.6"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}